[PATCH][RFC] Sanitize equals and hash functions in hash-tables.

[Martin Liška]

On 11/7/18 11:23 PM, Jeff Law wrote:
> On 10/30/18 6:28 AM, Martin Liška wrote:
>> On 10/30/18 11:03 AM, Jakub Jelinek wrote:
>>> On Mon, Oct 29, 2018 at 04:14:21PM +0100, Martin Liška wrote:
>>>> +hashtab_chk_error ()
>>>> +{
>>>> +  fprintf (stderr, "hash table checking failed: "
>>>> +	   "equal operator returns true for a pair "
>>>> +	   "of values with a different hash value");
>>> BTW, either use internal_error here, or at least if using fprintf
>>> terminate with \n, in your recent mail I saw:
>>> ...different hash valueduring RTL pass: vartrack
>>>                     ^^^^^^
>> Sure, fixed in attached patch.
>>
>> Martin
>>
>>>> +  gcc_unreachable ();
>>>> +}
>>> 	Jakub
>>>
>>
>> 0001-Sanitize-equals-and-hash-functions-in-hash-tables.patch
>>
>> From 0d9c979c845580a98767b83c099053d36eb49bb9 Mon Sep 17 00:00:00 2001
>> From: marxin <mliska@suse.cz>
>> Date: Mon, 29 Oct 2018 09:38:21 +0100
>> Subject: [PATCH] Sanitize equals and hash functions in hash-tables.
>>
>> ---
>>  gcc/hash-table.h | 40 +++++++++++++++++++++++++++++++++++++++-
>>  1 file changed, 39 insertions(+), 1 deletion(-)
>>
>> diff --git a/gcc/hash-table.h b/gcc/hash-table.h
>> index bd83345c7b8..694eedfc4be 100644
>> --- a/gcc/hash-table.h
>> +++ b/gcc/hash-table.h
>> @@ -503,6 +503,7 @@ private:
>>  
>>    value_type *alloc_entries (size_t n CXX_MEM_STAT_INFO) const;
>>    value_type *find_empty_slot_for_expand (hashval_t);
>> +  void verify (const compare_type &comparable, hashval_t hash);
>>    bool too_empty_p (unsigned int);
>>    void expand ();
>>    static bool is_deleted (value_type &v)
>> @@ -882,8 +883,12 @@ hash_table<Descriptor, Allocator>
>>    if (insert == INSERT && m_size * 3 <= m_n_elements * 4)
>>      expand ();
>>  
>> -  m_searches++;
>> +#if ENABLE_EXTRA_CHECKING
>> +    if (insert == INSERT)
>> +      verify (comparable, hash);
>> +#endif
>>  
>> +  m_searches++;
>>    value_type *first_deleted_slot = NULL;
>>    hashval_t index = hash_table_mod1 (hash, m_size_prime_index);
>>    hashval_t hash2 = hash_table_mod2 (hash, m_size_prime_index);
>> @@ -930,6 +935,39 @@ hash_table<Descriptor, Allocator>
>>    return &m_entries[index];
>>  }
>>  
>> +#if ENABLE_EXTRA_CHECKING
>> +
>> +/* Report a hash table checking error.  */
>> +
>> +ATTRIBUTE_NORETURN ATTRIBUTE_COLD
>> +static void
>> +hashtab_chk_error ()
>> +{
>> +  fprintf (stderr, "hash table checking failed: "
>> +	   "equal operator returns true for a pair "
>> +	   "of values with a different hash value\n");
>> +  gcc_unreachable ();
>> +}
> I think an internal_error here is probably still better than a simple
> fprintf, even if the fprintf is terminated with a \n :-)

Fully agree with that, but I see a lot of build errors when using internal_error.

> 
> The question then becomes can we bootstrap with this stuff enabled and
> if not, are we likely to soon?  It'd be a shame to put it into
> EXTRA_CHECKING, but then not be able to really use EXTRA_CHECKING
> because we've got too many bugs to fix.

Unfortunately it's blocked with these 2 PRs:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87845
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87847

I'm fine with having the patch in in next stage1 after the problems will
be fixed.

Martin

> 
>> +
>> +/* Verify that all existing elements in th hash table which are
> s/th/the/
> 
> 
> Jeff
>